The first time Morn walked into Quark's was around 2364, a time when he still had his hair. Quark thought he was just another customer passing through, when he sat down in what would soon be known as "his stool". Little did Quark know he would become such an important figure in his life, and to his bar. (DS9: "Who Mourns for Morn?")

After the Cardassians retreated from Bajor in 2369, Morn remained on Deep Space 9, which was then under Federation control. Morn spent most of his time at Quark's, becoming his most reliable customer and occasional business partner (notably in an attempt to setup an illegal Cardassian Vole fighting ring; he was discovered painting numbers on the voles, and the operation was stopped). (DS9: "Through the Looking Glass", "Emissary") Morn, while walking on the upper level of the Promende in 2369 viewed Lursa and B'Etor arriving on Deep Space 9. (DS9: "Past Prologue") In 2370, with his freighter rendered inoperable during a warp core retrofit, Morn was seen evacuating the station on the last available runabout, the USS Ganges, during the short-lived Bajorancoup. (DS9: "The Siege") In 2371, Morn sat near Tom Paris in Quark's and watched as Quark tried to scam EnsignHarry Kim into buying worthless Lobi crystals, which Quark said he got from a strange creature called a "Morn". (VOY: "Caretaker")

In the weeks leading up to the Dominion War, Morn went berserk after hearing Quark's prediction of the coming doom. He hit Quark with a barstool, and ran out of the bar and through the Promenade, screaming "We're all doomed!" He then ran into the Bajoran shrine, stark naked, and began crying to the Prophets for protection. (DS9: "Blaze of Glory")

Though he never spoke a word during the entire run of the series, it was a running gag that Morn was talkative and social. However, Morn did laugh in "The Nagus". This was the only time that he was depicted vocalizing on the series.

Morn attended the pre-wedding party thrown by Jadzia Dax in her quarters. He almost got into a fight with a Bolian, but the two managed to work things out. He eventually passed out behind the couch, leaving the following morning with an obvious hangover. (DS9: "You Are Cordially Invited")

The previous time Morn went away, Quark's sales dropped almost five percent. So, while he was gone, Quark created a hologram of the Lurian because his bar was incomplete without him. People loved Morn, and he felt that he was a mascot – everyone who came into the bar expected to see him, and if they didn't it didn't feel like home – which wasn't good for Quark's business.

After a period of over two weeks, the beets Morn had left in the cargo bay began to rot, causing Odo to seek him out in Quark's and ask that he remove them from the cargo bay. At the time, however, Morn was gone, and Quark had placed the hologram of the Lurian at "his stool", temporarily fooling Odo, to Quark's delight.

Morn's funeral display at Quark's (2374)

Moments later, Quark got word that Morn's cargo ship had been caught in an ion storm, where he had died. Following Morn's memorial, Quark learned from Benjamin Sisko, who unsealed Morn's will, that everything of Morn's was left to Quark: four cargo containers of beets, a mud bath "bed", a painting of a matador, and one-thousand bricks of gold-pressed latinum (in assay office locker 137).

It was later determined that Morn faked his own death, after the statute of limitations ran out against the Lissepian Mother's Day Heist, in order to throw his fellow thieves off his trail. In return for Quark's assistance in getting the four other thieves off of his back, he offered Quark a quantity of the latinum that he had hidden in his second stomach. (DS9: "Who Mourns for Morn?")

Morn was quite the ladies' man, and was often seen with a beautiful woman by his side. Morn once asked out Starfleet officer Jadzia Dax, who declined. She did say she thought he was cute, (DS9: "Progress") and, prior to 2372 later admitted that she used to have a little crush on him. As she explained it, however, he wasn't interested. (DS9: "Who Mourns for Morn?") Morn was also attracted to several other females aboard the station and was frequently seen flirting with some such as a Bajoran woman who received a hand kiss from him (DS9: "The Forsaken") as well as a female Kobheerian. (DS9: "Dramatis Personae")

In his guise as Morn, Mark Allen Shepherd receives directions from David Livingston

Morn was played by actor Mark Allen Shepherd. However, Ira Steven Behr once joked, "Actually, I play Morn. Marc Shephard is just an actor I've hired to confuse the fans at conventions... but don't tell anyone.... It's a secret...." Behr also referred to the character as "our favorite barfly." (AOL chat,1997)

Mark Allen Shepherd made his first appearance as Morn in DS9 series premiere "Emissary". In the episode "Who Mourns for Morn?", Shepherd, without the Morn makeup, briefly appeared as the Bajoran customer whom Quark asks to fill Morn's seat.

Morn was first identified by name in "Vortex" (although his name had previously been used in the scripts for "Dax" and "The Nagus") and by species in "Who Mourns for Morn?".

"Morn" is an anagram for Norm, the barfly played by George Wendt in the TV show Cheers. (Star Trek Encyclopedia (4th ed., vol. 2, p. 54)) The manner in which Dax shouts his name upon seeing the hologram at Quark's is reminiscent of the greeting Norm would usually receive as soon as he walked into Cheers.

It is possible that Morn was androgynous since Odo, while making an announcement to passers-by on the Promenade of Deep Space 9, said "Ladies and gentlemen (notices Morn walking by) ... and all androgynous species..." It is reasonable to assume Odo was making a joke at Morn's expense, though given the gravity of the situation, he could have been serious. The former seems to be true since Morn was referred to as he/him in subsequent episodes.

Before the series was aired, Morn was simply known by staff as "the Grinch". Mark Shepherd almost did not become Morn. Despite being hired for the role, the production crew accidentally left him off the calling list when they began filming "Emissary". By what Shepherd claims was intuition, he decided one day to wander onto the Paramount lot and see what was going on. Coincidentally that very day, Morn was to be filmed. Shepherd's contribution impressed the producers so much, he was made a recurring character. (The Making of Star Trek: Deep Space Nine)

According to Mark Shepherd, over the years a number of episodes were written during which Morn spoke various snippets of dialogue, but his lines were always removed by the time the script was being shot. In one particular example, Morn was to come down the spiral staircase in Quark's wearing a tuxedo, having been in the holosuite using the Julian Bashir, Secret Agentholoprogram. Quark is mixing a drink for Morn at the bar, and Morn looks over at him and says, "Shaken, not stirred." This scene remained through a number of script rewrites, to the point that Shepherd (in full Morn makeup) was actually fitted for a tuxedo, but at the last minute, the scene was removed. ("Morn Speaks", DS9 Season 7 DVD, Special Features) Shepherd also speculated, in a 1996 interview for Star Trek Monthly(citation needed • edit), that Morn would probably speak the last line of the series – but that was ultimately spoken by Quark.

Morn never spoke a single word throughout all of Deep Space Nine. In the German version of the episode "The Jem'Hadar", however, he does speak: he was just about to tell Quark what was troubling him when Quark simply walked away. Resigned, Morn mutters, "Dann nicht..." (roughly meaning "So much for that..."). These words are not uttered in the original English version.

With ninety-two appearances, Morn appeared in more episodes of Deep Space Nine than Jake Sisko (Cirroc Lofton), a regular cast member with only seventy-one appearances.

The character of Morn was, essentially, something of a gag that the program's producers were playing on just about everyone else. Though other characters repeatedly referred to him as being talkative and excitable, Morn was never actually shown doing anything other than imbibing, and quietly at that, at Quark's bar.

During the fifth season, Ron D. Moore in an AOL chat gave a summary of what was going on in the show, ending by joking that Morn had become President of the Federation. (AOL chat,1997) Moore later declined to comment on allegations that Morn had accepted illegal campaign contributions from the Ferengi or the Romulans, as a special counsel investigation on the matter was underway. (AOL chat,1997)

In the short story "Mirror Eyes," in the anthology Tales of the Dominion War, the narrator, a RomulanTal Shiar agent working undercover aboard DS9, identifies Morn as the only inhabitant of the station with whom she feels "an intellectual kinship."